In a blockchain, each block contains zero or more transactions. These transactions include data defined, at least in part, by the sender of the transaction. While this data is usually innocuous and relates to the execution of the transaction, it is possible for a malicious user to include data that may be offensive or illegal. Existing blockchains do not have ways of detecting such harmful data included in a transaction. If the transaction is otherwise valid and passes consensus, all blockchain participants will be, in turn, hosting a copy of this data whether it be valid or malicious. Since immutability is a property of blockchains, removing such harmful data from the transaction would be a benefit.